A new class of therapeutic agents has been designed incorporating the structural features of the potent 4-anilidopiperidine narcotic analgesics and the structural features of the 4-phenylazacycloheptanes which possess moderate analgesic activity and minimal opioid side effects. Therefore, it is proposed that the synthesis and pharmacological evaluation of a series of 1-subsituted-4-(propananilido) azacycloheptanes will result in the availability of highly potent analgesic agents having minimized opioid side effects, including little, if any, physical dependence capacity. In addition, selected 1-allyl and 1-(cyclopropylmethyl) -4-(propananilido)-azacycloheptanes will also be studied in an effort to develop mixed analgesic agonists-antagonists. In view of the potency-enhancing effects of 3-methyl substitution in the 4-anilidopiperidines and the 4-phenylazacyclo-heptanes a series of 1- substituted-3-methyl-4-(propananilido)-azacycloheptanes will also be prepared and pharmacologically evaluated. A study will also be carried out of the stereoselectivity of analgesic activity of the optical antipodes of the 1-substituted-4-(propananilido)azacycloheptane series. The results of this study should provide several new analgesic agents warranting further and more extensive biological screening and should also provide valuable information in the area of the development of potent analgesics of minimal abuse liability.